European Buckthorn is one of the most troublesome invasive
plant species in Wisconsin. As illustrated in the righthand portion of
the photo, it forms dense stands within existing native forests and displaces
nearly all native plant species with its dense growth. It produces numerous
black cherry-like fruits which are eagerly eaten by birds that carry the
seeds widely to infest other forests. Although it can invade nearly any
forest, the establishment and spread of European Buckthorn is dramatically
enhanced by opening the canopy and disturbing the soil as is done in the
construction of trails and roads through the forest. European
Buckthorn can be recognized by the thorns at the ends of the branches (see
photo) and by the abundant black fruits and the dark green leaves that persist
until mid to late November, often remaining conspicuous when other trees
are bare. There is also a closely related species called"Glossy
Buckthorn" (Rhamnus frangula)
which is equally invasive, but prefers wetter soils. It differs in having
no teeth along the leaf margins and in having shiny leaf surfaces, but produces
similar dense stands within our forests as well as in a variety of more
open sites.